PSI - Issue 12

T. Novi et al. / Procedia Structural Integrity 12 (2018) 145–164

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Author name / Structural Integrity Procedia 00 (2018) 000–000

Fig. 2. Section of the SAD; the heat sources are highlighted as dark items

to higher stress, these bearings will consequently generate more heat. It must also be said that the TCC will be higher due to a higher pressure acting on the various contacts which increases the contact area and thus allows greater heat exchange for conduction through the components of the di ff erential. This means that it is easier for heat to reach the components in contact with the external air and thereby making it less burdensome for the right side by lowering the temperature gradient. However, this e ff ect is at least an order of magnitude lower than having a higher load on the heat sources and, consequently, a larger amount of heat produced. For these reasons, the case which is considered for all calculations is the one with higher loads on the right side of the di ff erential (where the actuation and disc pack are places), so with the right wheel spinning at a slower rate. The chosen independent variables are pressure and relative rotational velocity between discs. Concerning pressure, the maximum actuation pressure is 20bar, so all the values of pressure from 1bar to 20bar are considered, with a discretization step of 1bar. Concerning the relative rotational velocity between discs ∆ ω , considering kinematic conditions the following equation has been found:

Vt r Rr

(8)

∆ ω =

where R is the curve radius (calculated as average of a skid pad). The conditions used to estimate the various thermal loads can be seen in table 2. 2.4.1. Primary heat sources The main source of heat present in the di ff erential is the disc pack. The amount of thermal energy produced by the discs is dependent on both the input variables: pressure and relative rotational velocity between discs. The relationship between the friction and heat generated by the clutch and the pressure in the piston chamber is quite clear. The same